1. Field of the Disclosure
Exemplary embodiments of the present disclosure relate to a liquid-droplet ejection head and a liquid-droplet ejection apparatus including the liquid-droplet ejection head, and more specifically to an inkjet head and an inkjet recording apparatus including the inkjet head.
2. Description of the Background
As one type of liquid ejection apparatus including a liquid ejection head, inkjet printers including inkjet heads are widely used because of their excellent image quality, low print cost, and wide product range from high-speed and high-priced printers to low-speed and low-priced printers. For such inkjet printers, there is strong market demand for even better image quality, cost reduction, and downsizing.
As a method of manufacturing an inkjet head, for example, micro-electro-mechanical systems (MEMS) technology is widely used. The MEMS technology is a fine processing technology involving semiconductor processing. For example, components of an inkjet head, such as a liquid chamber, a diaphragm, a piezoelectric element, and an electrode, are formed on a silicon substrate by etching, sputtering, or other processing. By reducing the sizes of those components or creating a better arrangement, the inkjet heads can be downsized. As a result, an increased number of heads can be produced from a single sheet of the silicon substrate. That is, as the size of the inkjet head is reduced, the production cost of the inkjet head is also reduced.
For downsizing of the inkjet head, one important challenge is to mount a driving integrated circuit (IC) for driving a piezoelectric element in the inkjet head in a more compact manner.
FIG. 1 is a schematic view of a configuration of a conventional type of inkjet head. As illustrated in FIG. 1, the conventional type of inkjet head has a head assembly 200 that includes a nozzle substrate 201 having nozzle orifices therein through which ink droplets are ejected, a chamber substrate 202 including liquid chambers to which ink is supplied under pressure generated by deformation of diaphragms with piezoelectric elements, a liquid supply substrate 203 having liquid supply passages therein through which ink is supplied to the liquid chambers, and a frame substrate 204. Further, a flexible printed circuit (FPC) 206 is electrically connected to the head assembly 200 by soldering or anisotropic conductive film (ACF) bonding, and driving integrated circuits (ICs) 205 for driving the piezoelectric elements of the chamber substrate 202 are bonded on the FPC 206.
In such a configuration, the FPC 206 may be shaken by the movement of the head and the bonding strength of the FPC 206 with the head assembly 200 may be weakened. Further, the above-described configuration takes up relatively much space, preventing downsizing.
To cope with such challenges, conventional techniques have been proposed that mount the driving ICs in a head assembly. For example, JP-2005-349712-A describes a configuration in which driving ICs are bonded on a piezoelectric-element substrate including piezoelectric elements.
In such a configuration, however, pressure chambers (substantially parallel to the diaphragms and piezoelectric elements) are arranged in series with ink channels and the driving ICs. Consequently, the total width of the inkjet head including the widths of those components is increased and relatively large.
By contrast, in conventional types of inkjet heads like those described in JP-3988042-B and JP-3580363-B, liquid chambers are arranged parallel to the driving ICs. Specifically, in JP-3988042-B, a sealing substrate is provided at the piezoelectric-element side of a channel formation substrate on which piezoelectric elements are formed, and the driving ICs are bonded on the sealing substrate. Alternatively, JP-3580363-B describes a configuration in which wire members for wire bonding extend outward from the driving ICs. Such a configuration can reduce the width of the channel formation substrate including liquid chambers.
However, for the above-described configurations, the sealing substrate or reservoir formation substrate on which driving ICs are mounted has a width including the widths of the driving ICs and reservoirs or the widths of piezoelectric elements and reservoirs. To suppress cross talk, the reservoir preferably has a large capacity, in particular, a capacity sufficient to reliably supply a certain maximum amount of ink flowing to the respective liquid chambers when ink droplets are simultaneously ejected from all channels. As the supply amount of ink decreases, the drive frequency is forced lower, significantly affecting ejection characteristics of the inkjet head. If the width of the reservoir is increased in consideration of such factors, the total width of the inkjet head is not reduced, resulting in increased cost.